import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Media[] ms = new Media[n];
        for (int i = 0; i < n; i++) {
            String type = sc.next();
            if (type.equals("book")) {
                ms[i] = new Book(sc.next(), sc.nextDouble());
            } else {
                ms[i] = new DVD(sc.next());
            }
        }
        double rent = MediaShop.calculateRent(ms, sc.nextInt());
        System.out.printf("%.2f", rent);
    }
}

/* 请在这里填写答案 */
class Media {
    String name;
    double price;
    public Media(String name) {
        this.name = name;
    }
    public double getDailyRent(int days) {
        return 1*days;
    }
    public Media(String name, double price) {
        this.name = name;
        this.price = price;
    }
}

class Book extends Media {
    public Book(String name, double price) {
        super(name, price);
    }
    public double getDailyRent(int days) {
        return price*0.01*days;
    }
}

class DVD extends Media {
    public DVD(String name) {
        super(name);
    }
    public double getDailyRent(int days) {
        return 1*days;
    }
}

class MediaShop {
    static double calculateRent(Media[] medias, int days) {
        double sum = 0;
        for (int i = 0; i < medias.length; i++) {
            sum += medias[i].getDailyRent(days);
        }
        return sum;
    }
}